A method of calibrating a parameter to measure the back electromotive force (BEMF) of a voice coil motor (VCM), and a method and apparatus to use the calibrating method to perform unloading control. The calibration method includes: reading servo data and measuring a BEMF value while seeking two predetermined points on a disk, and storing the servo data and the BEMF value, generating an actual velocity curve of a head using the stored servo data, and an estimated velocity curve of the head using the stored BEMF value and adjusting a parameter related to a BEMF measurement to align the actual velocity curve of the head with the estimated velocity curve of the head.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of calibrating a BEMF (back electromotive force), the method comprising: reading servo data and measuring a BEMF value while seeking two predetermined points on a disk, and storing the servo data and the BEMF value; generating an actual velocity curve of a head using the stored servo data, and an estimated velocity curve of the head using the stored BEMF value; and adjusting a parameter related to a BEMF measurement to align the actual velocity curve of the head with the estimated velocity curve of the head.
2. The method of claim 1 , wherein the generating of the actual velocity curve of the head uses a servo signal as a sampling interval to divide an obtained seek distance into seek time intervals, and is generated from calculated actual velocity values of the head.
3. The method of claim 1 , wherein the estimated velocity of the head is generated from an estimated velocity value of the head calculated by dividing a BEMF value measured in a VCM (voice coil motor) over a sampling interval by a BEMF constant to derive an estimated angular velocity value, and multiplying the estimated angular velocity value by a transforming proportional constant.
4. The method of claim 1 , wherein the parameter corresponds to a changing rate of a coil resistance value of a voice coil motor, and is varied to align the actual velocity curve of the head with the estimated velocity curve of the head.
5. The method of claim 1 , wherein the adjusting of the parameter includes calculating a ratio of the actual velocity curve of the head to the estimated velocity curve of the head, and adjusting a parameter related to the BEMF measurement to make the ratio approach 1 .
6. The method of claim 5 , wherein the ratio of the actual velocity curve of the head to the estimated velocity curve of the head is calculated as a ratio of a first harmonic sine coefficient of the actual velocity of the head to a first harmonic sine coefficient of the estimated velocity of the head.
7. A computer-readable recording medium having recorded thereon a computer program code to perform a method of calibrating a back electromotive force (BEMF), the method comprising: seeking two predetermined points on a disk to read servo data and measure a BEMF value, and store the servo data and the BEMF value; generating an actual velocity curve of a head using the stored servo data and an estimated velocity curve of the head using the stored BEMF value; and adjusting a parameter related to a BEMF measurement to align the actual velocity curve of the head with the estimated velocity curve of the head.
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August 1, 2007
August 31, 2010
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